Power supply



March'26, 1963 cs. K. TURNER 3,083,301

POWER SUPPLY Filed Dec. 1, 1958 GEORGE K. TURNER INVENTOR.

ATTORNEYS Unite tates l atent O 3,083,301 POWER SUPPLY George K. Turner, Paio Alto, Calif., assignor to Beckman Instruments, Inc., a corporation of California Filed Dec. 1, 1958, S631. No. 777,467 7 Claims. (Cl. 307-19) vide relatively constant current to the heaters of the associated tubes and the regulated high voltage may be employed as the plate voltage for the associated tubes.

It is a general object of the present invention to provide an improved low voltage, high current regulated power supply.

It is another object of the present invention to provide a power supply which supplies regulated low voltage, high current power and regulated high voltage.

It is another object of the present invention to provide a supply of the above character which employs in circuit a voltage regulator tube and at least one control transistor.

These and other objects of the invention will become more clearly apparent from the following description.

Referring to the drawing, the power supply includes a transformer 11 having a primary winding 12, and first and second secondary windings 13 and 14. The winding 13 is connected in a half wave rectifier circuit which includes the rectifier 15 and filter capacitor 16. The rec tifier circuit provides a source of unregulated D.-C. voltage to the voltage regulating device, which may be a voltage regulating tube 17.

An output reference voltage of reduced voltage is obtained from a resistive bridge which includes'a pair of arms comprising the resistors 19 and 21 and another pair of arms comprising resistor 22 and adjustable resistor 23. The two pairs of arms are joined by the resistor-18.

By suitably choosing the resistors which form the bridge 1 circuit, the high voltage is reduced to a level which corresponds to the desired regulated low output voltage at the terminals 29 and 30. By adjusting the relative values of the resistors in the bridge circuit, it is possible to compensate for voltage variations in the regulating tube due to line voltage variations and which variations are taken up by the resistor 18.

Regulated high voltage, determined by the voltage across the tube 17, is available at the terminals 27 and 28. The diiferenee between the regulated voltage across the tube 17 and the unregulated voltage is taken up by the resistor 18. As previously described, this voltage may be used to supply plate voltage to the tubes associated with a D.-C. amplifier or the like.

A full wave rectifier circuit provides power to the output terminals 29 and 30. The rectifier circuit comprises rectifying devices 31 and 32 and filter capacitor 33. One terminal of the rectifier circuit is connected directly to the output terminal 29 and also to the line 24. The other terminal of the rectifier circuit is connected to the output line 349 through the collector to emitter path of a series regulating transistor 34. When a load is placed across the terminals 29 and 30 the circuit of the emitter of transistor 54 is completed to the line 24 whereby the transistor 34 acts as an emitter follower.

A second transistor 35 is connected in cascade with ice the transistor 34. The emitter of the transistor 35 is connected to the base of the transistor 34 and the collector is connected in common with that of the transistor 34. The base voltage applied to the transistor 35 is derived from the voltage on the line 26.

The voltages available across the filter capacitors 16 and 33 are the line voltages times some constant which depends upon the turns ratio of the transformer and the drop in the rectifying devices. The voltage across the output terminals 29 and 30 is equal to the voltage between the lines 24 and 26 less a small constant voltage due to the base to emitter drop of the transistors 34 and 35 plus a small error due to line voltage variations.

The voltage on the line 24 is equal to the voltage at the line 28 times the ratio of the resistance of resistor 19 to the resistance of resistors 19 and 211. The voltage on the line 26 is equal to the voltage across the capacitor 16 (or the voltage at the line 28 minus the voltage across the resistor 18) times theratio of resistance of resistor 23 to the total resistance of resistors 22. and 23. The voltage between the line 26 and line 24 is equal to the difference of these voltages.

A pair of cascaded transistors is employed whereby the current drawn by the low voltage regulating circuit is minimum since only a relatively small change of current is required on line 26 to cause a relatively large change in current flowing through the cascaded transistor 34. Variations in regulating voltage due to changes in current is minimized.

Apparatus in accordance with the foregoing was constructed. The various components shown in the figure were as follows:

Transistors 34-2N 301A 35-2N 217 Tube: 17-OB2 Transformer:

Primary1l0/22O volts Secondary l t-30 volt CT, 550* ma. Secondary 13-11O volts, 15 ma. Rectifiers:

'15--Sarkes Tarzian 40K 31Sarkes Tarzian 10K 32--Sarkes Tarzian 10K Capacitors 16120 rnfd., 250 volts 33500 mfd., 25 volts- Resistors:

182.25K ohms 1975K ohms 21--9.1K ohms 2239K ohms 23-400 ohms A voltage regulator in accordance with the foregoing served to provide an output current of 0.5 amp. at a voltage of 10.7. The variation in output voltage was less than 0.2% for line voltage variations between and volts. The output voltage varied less than 1% for output current variations between 0.46 and 0.56 ampere.

Thus, it is seen that there is provided in combination a high voltage regulating device, for example, an inexpensive voltage regulating tube which acts as a reference for both the high voltage available at one pair of terminals, and for low voltage power available at another pair of terminals. A bridge circuit compensates for residual variations in output voltage of the low voltage circuit resulting from imperfect operation of the voltage regulator tubes, and the finite gain of the transistor regulators. A relatively inexpensive circuit which provides good high voltage and low voltage regulation is provided.

I claim:

1. A power supply comprising a first source of D.-C. voltage, a voltage regulating means connected to receive said D.-C. voltage and provide a regulated voltage, a second source of D.-C. voltage adapted to provide low voltage output power, a series regulating transistor having base, emitter and collector electrodes connected with the emitter. and collector in series with the output from said second source, a bridge network connected to re voltage serving to provide low voltage output power, a

series regulating transistor having base, emitter and collector electrodes connected with the emitter and collector in series with the output from said second source, a

second transistor having base, emitter and collector electrodes connected in cascade with said first transistor and serving to control the base current in the same, a bridge network connected to receive the regulated voltage and serving to provide a portion of said voltage across a circuit including the base of said second transistor.

' 3. A power supply comprising a first source of unregulated D.-C. voltage, a voltage regulating means connected in circuit with said first source of unregulated -D.-C. voltage and serving to provide a regulated voltage, a second source or unregulated D.-'C. voltage, first and second output terminals connected to receive power from 'the second source, a series regulating transistor having base, emitter and collector electrodes connected with the emitter and collector electrodes in series with said first output terminal, a second transistor having base, emitter and collector electrodes connected in cascade with said first transistor and serving to control the base current flowing in the same, a first voltage divider connected to receive the regulated voltage and provide :a portion of said voltage to the base of said second transistor, and a second voltage divider connected to the regulated volt age source and being connected to the second output terminal.

4. A power supply as in claim 3 wherein said voltage regulating means comprises a voltage regulating tube and additional output terminals serving to provide a regulated voltage output from said voltage regulating tube.

4 5. A power supply comprising a first source of unregulated D.-C. voltage, a voltage regulating means connected to receive said unregulated voltage and provide a regulated voltage, a second source of unregulated D.-C.

voltage serving to provide low voltage output power, a

series regulating transistor having base, emitter and collector electrodes connected with the emitter and collector in series with the output from said second source,

a second transistor having base, emitter and collector,

electrodes connected in cascade with said first transistor and serving to control the base current in the same, a resistive bridge circuit connected to receive the regulated voltage and serving to provide a voltage across a circuit including the base of said second transistor, said bridge circuit serving to correct for residual variations due'to imperfect operation of the voltage regulating means and the finite gain of the transistor regulator.

'6. A power supply comprising a first source of unregulated D.-C. voltage, means for regulating said first source of unregulated D.-C. voltage to provide a first source of regulated D.-C. voltage, serving to provide a low voltage output, variable impedance means connected to said low voltage output serving to regulate the same, a bridge circuit having a first pair and a second pair of terminals to receive the first regulated voltage and the first unregulated voltage respectively and serving to provide a reference input to said variable impedance at the output, said first and second pairs of terminals including one common terminal, said bridge circuit serving to correct for variations due to imperfect operation at said first source of regulated D.-C. voltage.

7. Apower supply comprising a first source of unregulated D.-C. voltage, means for regulating said first source of unregulated D.-C. voltage to provide a first source of regulated DEC. voltage, a'source of D.-C.

voltage adapted to provide low voltage output, variable impedance means connected to said low voltage output,

and a bridge network means connected to receive said first unregulated voltage and said regulated voltage and serving to provide a predetermined fraction of the difference of said voltages as a reference to said variable impedance means.

References Cited in the file of this patent UNITED STATES PATENTS 2,850,694 Hamilton Sept. 2, 1958 2,855,559 Goodrich Oct.- 7, 1958 2,885,626 McNamee May 5, 1959 MoNamee Nov. 10, 1959 

1. A POWER SUPPLY COMPRISING A FIRST SOURCE OF D.-C. VOLTAGE, A VOLTAGE REGULATING MEANS CONNECTED TO RECEIVE SAID D.-C. VOLTAGE AND PROVIDE A REGULATED VOLTAGE, A SECOND SOURCE OF D.-C. VOLTAGE ADAPTED TO PROVIDE LOW VOLTAGE OUTPUT POWER, A SERIES REGULATING TRANSISTOR HAVING BASE, EMITTER AND COLLECTOR ELECTRODES CONNECTED WITH THE EMITTER AND COLLECTOR IN SERIES WITH THE OUTPUT FROM SAID SECOND SOURCE, A BRIDGE NETWORK CONNECTED TO RECEIVE SAID REGULATED VOLTAGE AND SERVING TO PROVIDE A PREDETERMINED FRACTION OF SAID REGULATED VOLTAGE ACROSS A CIRCUIT INCLUDING THE BASE OF THE SERIES REGULATING TRANSISTOR. 